The limited availability of donor hearts for people with end stage heart failure has driven the continual development of mechanical circulatory support systems (MCSSs). MCSSs can be broadly classified into pulsatile and continuous flow systems. Pulsatile systems drive blood indirectly through blood pumps, resulting in minimal blood trauma. This disadvantage of these systems, however, is their relatively large size. Continuous flow systems offer smaller size and simplicity, but with a flow driver that directly contracts blood, resulting in increased tendency toward thrombosis and hemolysis. The MCSSs described here can potentially combine the blood compatibility of pulsatile MCSSs with much of the simplicity and small size of continuous MCSSs. The proposed device modifies our existing electrohydraulic TAH. [proprietary information intentionally deleted] The device operates as a simpler, low stroke volume and high beat rate pump, which can deliver up to 12 L/min against a 100 mmHg afterload, and has the potential to be 1/2 the size of existing pulsatile systems. Phase I studies will focus on complete in vitro characterization of the device, incorporation of Starling-like flow control, and preliminary in vivo evaluation. Phase II studies will focus on miniaturization and further in vivo characterization, including studies of nonpulsatile versus pulsatile circulatory support. PROPOSE COMMERCIAL APPLICATION: The potential application will be to the more than 40,000 people who die of congestive heart failure annually. Commercial applications of the device being developed will expand from those currently envisioned for existing VASs and TAHs principally because of the increased simplicity and decreased size, without compromise in blood compatibility.